Adapt vfs kqfilter to the shared vnode lock used by zfs write vop. Use

vnode interlock to protect the knote fields [1]. The locking assumes
that shared vnode lock is held, thus we get exclusive access to knote
either by exclusive vnode lock protection, or by shared vnode lock +
vnode interlock.

Do not use kl_locked() method to assert either lock ownership or the
fact that curthread does not own the lock. For shared locks, ownership
is not recorded, e.g. VOP_ISLOCKED can return LK_SHARED for the shared
lock not owned by curthread, causing false positives in kqueue subsystem
assertions about knlist lock.

Remove kl_locked method from knlist lock vector, and add two separate
assertion methods kl_assert_locked and kl_assert_unlocked, that are
supposed to use proper asserts. Change knlist_init accordingly.

Add convenience function knlist_init_mtx to reduce number of arguments
for typical knlist initialization.

Submitted by:	jhb [1]
Noted by:	jhb [2]
Reviewed by:	jhb
Tested by:	rnoland

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/kern/uipc_mqueue.c b/sys/kern/uipc_mqueue.c
index 2a5028c..69bf59c 100644
--- a/sys/kern/uipc_mqueue.c
+++ b/sys/kern/uipc_mqueue.c
@@ -1531,8 +1531,8 @@ mqueue_alloc(const struct mq_attr *attr)
 		mq->mq_msgsize = default_msgsize;
 	}
 	mtx_init(&mq->mq_mutex, "mqueue lock", NULL, MTX_DEF);
-	knlist_init(&mq->mq_rsel.si_note, &mq->mq_mutex, NULL, NULL, NULL);
-	knlist_init(&mq->mq_wsel.si_note, &mq->mq_mutex, NULL, NULL, NULL);
+	knlist_init_mtx(&mq->mq_rsel.si_note, &mq->mq_mutex);
+	knlist_init_mtx(&mq->mq_wsel.si_note, &mq->mq_mutex);
 	atomic_add_int(&curmq, 1);
 	return (mq);
 }